The present invention generally relates to a flow control device for dough and related viscous foodstuffs, and more particularly to a metering device that employs a centerless helix member to portion out precise quantities of dough for subsequent use in bread and related baked goods.
The use of pumps and conveyors for moving and metering large quantities of dough are well-known in the art. Typically, such devices accept a dough mixture from a hopper, then transport it with either an auger mounted to a screw-like shaft housed in a closed or semi-closed tubular chamber, or a lobe-like intermeshed positive-displacement pump connected to a discharge conduit. In either situation, the dough is typically pumped and discharged to a moving conveyor, which takes the dough to a divider for cutting and subsequent processing. Metering, or the ability to divide the dough up into discrete quantities, can be incorporated into either approach; in the former case, a separate paddle or knife can be added, set to deploy during preset intervals, while in the latter case, the very nature of a positive displacement pump that operates on a fixed quantity of dough lends itself to metering functions when combined with an appropriate discharge conduit. This capability gives such pumps the ability to portion discrete amounts of dough, rather than more massive continuous quantities, which can be beneficial in situations that require consistent, repeatable dough portions. Devices that provide this additional metering, or dividing of dough are also well-known in the art.
However, each of these approaches have disadvantages. With the shaft-mounted auger approach, the dough has a tendency to stick to the center shaft, resulting in handling difficulties and inconsistent quantities being dispensed, as well as more costly downtime for cleaning and maintenance. Large, wetted surface areas with regions of little or no flow that are not problematic with low viscosity fluids (such as water) become xe2x80x9ctrapsxe2x80x9d for stickier, more flow-resistant substances. Such surface configurations are prevalent in shaft-mounted auger systems. For example, shank portions connecting the base of the auger to the shaft often cannot generate enough movement, especially at low shaft revolutions per minute (rpm) to keep dough buildup from occurring. Consequently, without a continuous purging action, the buildup of dough can congeal, thus clogging up the auger and discharge conduit. In addition, the greater resistance to flow caused by the buildup necessitates higher power motors to run the auger, as well as reduced throughput due to increased flow obstruction. With the positive-flow pump-based process, which relies on a constant volume basis for the dispensing of accurate dough quantities, the addition of yeast in the dough produces density variations due to gas byproduct formation, which can cause weight discrepancies in the divided-up dough, making it more difficult to produce uniform products. Moreover, shearing and compacting forces imparted on the dough by the pump causes increased temperature and pressure profiles within the dough, which can adversely effect the dough""s subsequent utility as an edible final product. The active nature of the dough, caused by the aforementioned addition of yeast, presents other challenges to dough handling devices, not the least of which is the rapidity with which dough must be moved. This need for speed and high throughput in dough handling is often at odds with a need to keep the work performed in the dough low during metering and transport.
In other types of dough compositions (such as cookie dough), where yeast is not included, the consistency is such that once the dough is compacted (such as due to pumping), it becomes difficult to transport or meter, as it hardens and can""t readily be made to revert back into its pre-compacted state. The conventional screw and positive displacement pump systems, by virtue of the work they do on the dough, are largely responsible for the creation of this undesirable condition. Edible additives to the dough (such as nuts, chocolate chips, decorations and the like) exacerbate dough transport and metering in conventional screw- or pump-based systems. In one regard, the additives act as reinforcing members, giving the dough a quasi-composite consistency, which tends to increase its resistance to flow. In another regard, the conventional screw and pump systems may slice up the additives, thus reducing the quality and subsequent appeal of the dough to a potential consumer.
Consequently, what is needed is a dough metering system that promotes consistent, reliable metering while simultaneously minimizing temperature and pressure elevations in the dough. What is also needed is a dough metering system that can meet the above needs for various dough compositions.
This need is met by the present invention wherein a dough feeder system meters precise amounts of dough without the disadvantages of the prior art. In accordance with one embodiment of the present invention, a dough transport system is disclosed. The system includes a dough feeding unit and a conveyor unit. The dough feeding unit includes a primary support structure, a motor coupled to the primary support structure, a hopper with dough input and output openings, an effluent housing comprising inlet, outlet and center sections, and a centerless helix with proximal and distal ends. The centerless helix is disposed within and extends through the effluent housing, and is rotatably responsive to the motor through a coupling at the proximal end of the centerless helix. The helix defines an axis of rotation along its centerline. The proximal end of the centerless helix includes either a flattened portion to promote secure, thorough mounting to a rotatable coupling disposed within an endwall of the effluent housing, or is coupled to a stub shaft, which itself is rotatably mounted to an endwall in the effluent housing. The endwall of the effluent housing is in axial alignment with the centerline of the centerless helix. The effluent housing is adjacent the hopper and mounted to the primary support structure. Its inlet section is aligned with the dough output opening of the hopper, while its outlet section is aligned to dispense a metered dough portion to the conveyor unit. Preferably, the alignment between the effluent housing inlet section and the hopper dough outlet opening is a vertical alignment to encourage gravity feed from the latter to the former. The center section is disposed between the inlet section and the outlet section, and connects the two. The conveyor unit is operably mounted in relation to the outlet section of the effluent housing, and is used to carry away metered dough portions being discharged from the effluent housing. The construction and movement of the dough feeder unit is such that a continuous dough path from the hopper through the effluent housing is effected, and upon placement of a quantity of the dough in the hopper and selective rotation of the centerless helix, a discrete quantity of dough is metered and deposited upon the conveyor unit without an appreciable rise in pressure or temperature due to the action of the dough transport system. The dough transport system can be configured to operate in either a continuous mode, where variable helix speeds may be employed to control dough flow rate, or in an intermittent mode, where the stop/start sequence produces discrete dough chunks.
Optionally, the dough transport system includes the use of food-grade stainless steel or related material for the surfaces of the hopper, effluent housing and centerless helix. The dough transport system can also include a torque-limiting device as a safety measure to protect the system in the event a flow obstruction arises during system operation, or a foreign object becomes lodged somewhere in the dough flowpath. The effluent housing further comprises a discharge liner disposed within the effluent housing. Such liner could be made of an abrasion-resistant ultrahigh molecular weight (UHMW) polyethylene to minimize the likelihood of metalto-metal contact between the helix and the inner walls of the effluent housing.
In addition, a motor controller can be included to limit the power output of the motor. In a preferred embodiment, the controller can limit power output to a maximum of approximately 1 horsepower. This can be valuable in situations where an oversized motor used to drive the helix needs to conform to the low-power requirements of the dough being transported. Either cumulatively or in the alternative, the maximum power output of the motor used in the system may be limited to approximately 1 horsepower. In contrast to conventional motors, which are typically sized in the 15 to 30 horsepower range in order to drive a screw auger or positive displacement pump, an may generate internal pressures within the dough of upwards of 20 to 30 pounds per square inch (psi), the low power motors used in conjunction with the present invention, with the relatively shear-free movement and metering of the dough inherent in the centerless helix approach, will ensure that such pressures are not generated in the dough, and that resulting premature dough processing is avoided. The high pressure levels exhibited by the larger horsepower motors, if left unabated, would impart significant work on the dough. A variable-frequency speed control may also be used to provide adjustable dough feed rates. To facilitate the positioning of the dough feeding unit relative the conveyor unit, casters may be disposed on a lower surface of the primary support structure, thus enhancing its mobility.
In accordance with another embodiment of the present invention, a dough feeding unit is disclosed. The dough feeding unit includes a primary support structure, motor, hopper, effluent housing and centerless helix in a configurationally similar approach to that of the dough feeding unit portion of the previous embodiment. The flexible, portable nature of the dough feeding unit permits it to be placed in proximity with a conventional conveyor system, capable of a variety of operational speeds that are compatible with conveyor motion.
Optionally, the dough feeding unit includes the use of food-grade stainless steel or related material for the surfaces of the hopper, effluent housing and centerless helix in a manner similar to that of the previous embodiment. It can also include a torque-limiting device as a safety measure, as well as a discharge liner disposed within the effluent housing, both similar to that of the previous embodiment. In addition, a motor controller can be included to limit the power output of the motor, or have a maximum motor power output of not more than approximately 1 horsepower, which, also like the previous embodiment, may include variable-frequency speed control to provide adjustable dough feed rates. To facilitate the positioning of the dough feeding unit, casters may be disposed on a lower surface of the primary support structure, thus enhancing its mobility.
In accordance with yet another embodiment of the present invention, a method of metering dough is disclosed. The method includes loading a mass of dough into a hopper; rotatably operating a centerless helix disposed within an effluent housing, where the effluent housing is disposed adjacent to and in dough communication with the hopper; accepting at least a portion of the mass of dough into an aperture disposed in an input section of the effluent housing; and adjusting the rotational speed of the centerless helix such that the mass of dough exiting an output section of the effluent housing is divided into at least one metered portion, where the at least one metered portion exhibits no appreciable temperature or pressure rise over the mass of dough being loaded into the hopper.
Optionally, a motor may be rotatably connected to the centerless helix to provide rotational movement thereto. The centerless helix may be operated in a variable speed mode to control the flow rate of the dough, or may be operated in an intermittent xe2x80x9cchunkerxe2x80x9d mode, where by alternately stopping and starting the motor in response to rotational input from a sensor, discrete dough portions, or chunks, can be formed. In addition, the motor may have a maximum power output not in excess of 1 horsepower, thus enabling the use of a smaller, less costly helix turning power supply. In addition, the effluent housing can be lined with a discharge liner to prevent direct contact between the helix and the effluent housing, and the discharge liner can be made from an ultrahigh weight molecular polymer. As an additional step, the metered dough portions can be deposited onto a conveyor to facilitate movement of the metered dough to another location. A variable frequency speed controller may be connected to the conveyor to vary the speed the metered dough is carried away by the conveyor. A motor controller can also be used to limit motor horsepower, thus ensuring that undue work on the dough is not performed, and that excess driving motor power is not being inefficiently used. As with the previous embodiments, a torque-limiting device, such as in the form of a slip clutch, can operate to protect the motor and helix.
Other objects of the present invention will be apparent in light of the description embodied herein.